Find the sum of the first 50 terms of the arithmetic sequence if the first term is 21 and the twentieth term is 154.​

Answers

• Réponse publiée par: shannel99

  9625

  Step-by-step explanation:

  for an arithmetic sequence

  ●an = a + (n-1) d

  ●sn = n/2[2a + (n-1)d]

  where is the first term and d the common difference we require to find d

  given: a=21 then

  a20=21 + 19d = 154

  19d = 154 - 21 = 133 d= 133/19 = 7

  s50 = 50/2 [(2x21) + (49×7)]

  =25(42 + 343)

  =25 × 385=9625
• Réponse publiée par: elaineeee

  answer:

  50th term is D. 9625 Explanation:

  for an arithmetic sequence

  ∙xan=a+(n−1)d∙xSn=n2[2a+(n−1)d

  ]

  where a is the first term and d the common difference

  we require to find d

  given

  a=21 then

  a20=21+19

  d=15419

  d=154-21=133

  ⇒

  d=13319=7

  S50=502[(2×21)+(49×7)]

  ×=25(42+343)×=25×385=9625
• Réponse publiée par: villatura

  b.9765

  Step-by-step explanation:

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• Réponse publiée par: hajuyanadoy

  find the sum of the first 50 terms of the arithmetic sequence if the first term is 21 and the twentieth term is 154

  answer

  9625

  Step-by-step explanation:

  for an arithmetic sequence

  ●an = a + (n-1) d

  ●sn = n/2[2a + (n-1)d]

  where is the first term and d the common difference we require to find d

  given: a=21 then

  a20=21 + 19d = 154

  19d = 154 - 21 = 133 d= 133/19 = 7

  s50 = 50/2 [(2x21) + (49×7)]

  =25(42 + 343)

  =25×385=9625
• Réponse publiée par: saintjohn

  Hope this helps!

  #CarryOnLearning

  
  
• Réponse publiée par: reyquicoy4321

  Step-by-step explanation:

  9625

  I used other steps. Since first term is 21 and 20th term is 154 its common difference was 7. Using 49 multiplied to 7 and adding 21 you can get the last term 364.By adding last and first and multiply it by 25 you can get the sum of 9625. Hope this helps.